Rock sea-lavenders description

The rock sea-lavenders comprise a group of closely related, beautiful (1) and delicate (2) plants that have cushions of leaves close to the ground, from which arise branched flowering stems that may be delicate or robust, short or tall, but in all cases support numerous spikes of attractive bluish-lilac coloured flowers (1)(2). In high summer, when flowering en masse, these plants can give a striking purplish 'haze' to the places in which they grow. Almost all of the species that occur in Britain and Ireland are endemics; they are found no-where else in the world (1).

Related species

Rock sea-lavenders biology

In 1986 the taxonomy of the rock sea-lavenders was revised (6), nine species are now recognised, along with a large number of subspecies(2). However, the species are notoriously difficult to tell apart (2). Although there is some geographical separation of the various species and subspecies, this is by no means an accurate or reliable method of distinguishing between them (2). Indeed, there are a number of 'hot spot' areas where one can find several species or sub-species growing together (e.g. on the Carboniferous limestone of south Pembrokeshire, the cliffs of Quaternary head deposits of south Devon, and the chalk and limestone cliffs of Dorset). Rock-sea lavenders are perennial, and reproduce asexually through a process known as 'apomixis'. Flowers are produced from June to September (5).

Rock sea-lavenders range

Current knowledge of the distribution of our endemic rock sea-lavenders is patchy (3). L. paradoxum, L. parvum, and L. transwallianum are all restricted to Pembrokeshire. L. britannicum and L. procerum are fairly widespread along the western coast of Britain, and L. procerum also occurs on the east coast of Ireland (7). L. dodartiforme is confined to Dorset, L. loganicum is known only from Cornwall, and populations of L. recurvum occur in Dorset, Cumberland and Wigtownshire (4). L. binervosum is not endemic to the UK; it is also known from parts of Europe (5), but four subspecies of binervosum are endemic to Britain and Ireland (7).

Rock sea-lavenders threats

Many populations of rock sea-lavender in the UK are not under any immediate threat. However, some may be vulnerable to trampling (4), while several dune-slack, sea-wall and cliff populations are known to have been lost, at least temporarily, as a result of dune movements, the construction of new sea defences and coastal landslips (7). Many colonies are small (which increases their vulnerability), and collecting is thought to have posed a threat to a few species (particularly L. recurvum) in the past (4).

Rock sea-lavenders conservation

Many populations occur within Sites of Special Scientific Interest (SSSIs), and two populations of L. parvum occur within National Nature Reserves (NNRs) (2). Together, the Botanical Society of the British Isles (BSBI) and the National Trust coordinate the conservation actions outlined in the UK Biodiversity Action Plan for Britain's endemic rock sea-lavenders (2). The BSBI have carried out an extensive mapping scheme, which will be of enormous help as it will allow areas needing further research to be prioritised and will also aid in the initiation of a monitoring programme (2).

The UK Biodiversity Action Plan for this species is available at UK BAP.

Authentication

Glossary

Asexually

Of asexual reproduction: reproduction that does not involve the formation of sex cells ('gametes'). In many species, asexual reproduction can occur by fission (or in plants 'vegetative reproduction'); part of the organism breaks away and develops into a separate individual. Some animals, including vertebrates can develop from unfertilised eggs, this process, known as parthenogenesis gives rise to offspring that are genetically identical to the parent

Carboniferous

A geological period, the penultimate period of the Palaeozoic Era, 360-286 million years ago. The carboniferous comes after the Devonian and before the Permian.

Colony

A group of organisms living together, individuals in the group are not physiologically connected and may not be related, such as a colony of birds. Another meaning refers to organisms, such as bryozoans, which are composed of numerous genetically identical modules (also referred to as zooids or 'individuals'), which are produced by budding and remain physiologically connected.

Dune slacks

Depressions between sand dunes that are often wet during the winter.

Endemic

A species or taxonomic group that is only found in one particular country or geographic area.

Perennial

Plants that live for at least three seasons; after an initial period they produce flowers once a year.

Quaternary

A geological time period, part of the Cenozoic Era, covering the last 2 million years.

Subspecies

A different race of a species, which is geographically separated from other populations of that species.

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